A three-unit-based approach in coastal-change studies using Landsat images

An understanding of a dynamic coast requires long-term investigation of changes taking place along its shoreline. Multi-date satellite images can be used to highlight long-term coastal behaviour. In the present study, a new methodology has been suggested, by proposing initial selection of three basic coastal units, namely, 'land', 'wetland' and 'water'. These three coastal units have been used for identification of five different 'change units', namely, 'land replaced by water', 'land replaced by wetland', 'wetland replaced by water', 'land accretion' and 'wetland accretion'. Based on this proposed approach, a case study has been carried out along the coastal area covering parts of West Bengal and Orissa states of eastern India using Landsat images. The derived coastal changes demarcated using satellite images have been verified by field checks. Further, these changes have been used to study three important coastal issues: sediment budget, coastal morphodynamics and hazard-zonation mapping. This study shows that consideration of three basic coastal units is an appropriate choice for studying long-term coastal changes using multi-date satellite data.